Having rebounded from a 5-9 start to push Miami within a game of elimination in last year’s playoffs, a veteran team like the Celtics isn’t about to push the panic button. But their confidence is in dire need of a boost after their 20-point loss at lowly Detroit, a result that exposed a surprising lack of grit.

Most notable through 11 games is the deterioration of Boston’s vaunted defense. The Celtics are 22nd in defensive efficiency after placing first last season and never having finished worse than fifth since Kevin Garnett prior to the 2007-08 season .

Their main problem appears to be that KG can’t play 48 minutes. The Celtics allow only 94.6 points per 100 possessions when he plays and 114.2 when he sits. Those figures would rank first and last in the league, respective, if applied to full games. But he couldn’t do that in his prime, let alone at 36, so head coach Doc Rivers has to figure out a way to not get destroyed in the 20 minutes Garnett doesn’t play while keeping him fresh for the postseason. (Perhaps Gregg Popovich has a thoughts on the subject for his old point guard?)

The Celtics had been pegged as one of the deeper teams in the league with the additions of Jason Terry, Courtney Lee and Jared Sullinger. But their reserves have been below average at best, mitigating the work of a starting unit that ranks seventh in scoring differential. Their plight is embodied by forward Jeff Green, whose 9.7 player efficiency rating stands in stark contrast to the $36 million extension he signed last summer.

Garnett, 10-time All-Star Paul Pierce (19.3 points per game, 39.2 % on 3-pointers) and especially Rajon Rondo, the league leader in assists, can still do a ton of damage. Without better defense and more support, however, this could finally be the year Boston’s window closes for good.

* In addition to his superlative playmaking — see below — Rondo’s outside shooting has improved tremendously. While it’s still too early to tell if he’s made a permanent addition to his game, Rondo is shooting 50 percent from 16-23 feet, tied for fourth among players with at least four attempts per game.

* Pierce has been hampered by a bum ankle, but the news that Kawhi Leonard and Stephen Jackson are out should aid the healing process. The Spurs have generally held up well against Pierce in recent years, holding him to 14.8 points over the past six meetings. Extending that streak will be a tough task without their top two defensive options.

Key number

34 – Rondo’s streak of games with at least 10 assists, the third-longest in NBA history. He trails only Magic Johnson (46, 1983-84) and John Stockton (37, 1989). Rondo is on pace to tie Johnson in San Antonio on Dec. 15 and surpass him in Chicago on Dec. 18. In addition, his current assist average of 13.1 per game would be the NBA’s highest since Stockton averaged 13.73 in 1991-92.